Field of Invention
The present disclosure relates to a material structure and, in particular to a thermoelectric material structure.
Related Art
In the recent years, the issues of environmental warming and environmental awareness have been paid attentions, and the research topics about how to save energy and improve energy efficiency are accordingly very popular. “Thermoelectric material” is a functional material capable of converting thermal energy into electrical energy without the assistance of other specific external forces or mechanical parts. In the current industries, thermoelectric materials can be used in the applications such as thermoelectric coolers, semiconductor chip cooling, thermoelectric generators, space applications, or other thermoelectric energy conversion.
The energy conversion efficiency of thermoelectric materials generally depends on the thermoelectric figure of merit (ZT), which is shown as the follow equation:
  ZT  =                              α          2                ⁢        σ            k        ⁢    T  
Wherein, α is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity, which is the sum of the electron thermal conductivity ke and the phonon thermal conductivity kL, and T is the operating temperature (absolute temperature). When the ZT is higher, the better the performance of the thermoelectric material and the higher the thermoelectric conversion efficiency.
According to the above equation, the ZT value can be increased by increasing the Seebeck coefficient α and/or the electrical conductivity σ, or by reducing the thermal conductivity k. In the conventional art, the ZT value is usually increased by increasing the Seebeck coefficient α or the electrical conductivity σ. In practice, when increasing the Seebeck coefficient α, the ZT value can be obviously increased.